A quantitative investigation of distortion of polylactic acid/PLA) part in FDM from the point of interface residual stress

In order to reveal the distortion mechanism of PLA part, the bilinear elastic-softened cohesive model is adopted and the micromechanics is utilized for the first time to describe the interface state. The residual stress models of the elastic interface state, elastic-softened state, and the elastic-softened-de-bonding interface state are established quantitatively according to the cohesive zone model to investigate the relationship between building parameters and residual stress, respectively. An experimental is proposed to validate the theoretical residual models. The experimental results indicate that the layer thickness plays the dominant role in determining the distortion compared with deposition velocity. The distortion of PLA part is mainly caused by accumulation of residual stresses resulting from non-uniform temperature gradients in continuous heating and cooling cycles. The temperature of the filament with different building parameters in the fabrication process is collected to observe the relationship between part distortion and temperature and the temperature files show a good accordance with the distortion trend. The qualitative analyzed results of the residual stress models also coincide with the experimental results well, which indicates the effectiveness of the residual stress model and shows that it can express the distortion mechanism well.